The Corneal Epithelial Thickness Profile in a Healthy Saudi Population

Epithelial mapping appears to be a valuable technique for a corneal and refractive surgeon, useful for distinguishing corneas with the true presence of corneal ectasia from those that are suspicious. Interpreting the epithelial thickness map data requires an understanding of corneal epithelial thickness (CET) normal values and variable patterns. Unlike corneal thickness, epithelial thickness assessment with anterior segment optical coherence tomography (AS-OCT) seems to be influenced by gender and age. The study aimed to investigate the detailed mapping of CET characteristics in normal eyes from the Saudi population and to assess its variation with age and sex using anterior segment 7-mm-wide OCT (AS-OCT) scans.

Regional epithelial thickness was assessed using an anterior radial scanning protocol with REVO NX (Optopol Technology S.A, Zawiercie, Poland) in 596 eyes of 298 individuals aged 10 to 98. CET maps in a 7 mm diameter were automatically generated by the built-in software, displaying thickness in 17 sectors divided into three zones, i) a central zone within the 0-2 mm diameter, ii) ring 1 zone, a paracentral (P-CET) zone from 2 to 5-mm, and iii) ring 2 zone, a midperipheral zone (MP-CET) from 5 to 7 mm. Ring 1 and 2 zones were further divided into eight sectors each, including superior (S), inferior (I), nasal (N), temporal (T), superonasal (SN), inferonasal (IN), superotemporal (ST), and inferotemporal (IT). An analysis was done on correlations between age and gender and the CET across different zones.

Males and older adults had a substantially thicker CET than females and younger participants, with the C-CET measuring 59.2±4.5µm. In three zones, no interocular asymmetry was seen. Superiorly, CET is significantly thinner than inferiorly (p<0.05), with temporal zones being thinner than nasal zones (p<0.05). The C-CET increases with age in the seven groups of both genders, but its dependence on age is weaker in paracentral sectors; C-CET was 3.5% thicker in males. Paracentral nasal and inferior zones showed 2.2-3.6% thicker CET while the superior and temporal paracentral zones showed 3-5% thicker CET among males compared to females.

From 17 CET zones of central 7 mm cornea the C-CET was affected by gender and age. The CET distribution in these healthy Saudis' eyes was non-uniform with the CET being thinner in the superior cornea. This finding could aid in predicting corneal diseases and planning refractive procedures.